ICAR AICE-JRF/SRF (PhD) — Food Processing Technology, Food Safety & Quality, Processing and Food Engineering · India · ICAR through the National Testing Agency
Original practice questions written to the published syllabus · not past papersMass and energy balances and the three transfer processes — momentum, heat and mass — applied to foods: pumping viscous products, heating cans and pouches, and moisture and gas movement through foods and packaging films.
In the exams: GATE XE-G Section 4 (mass and energy balance, momentum transfer, heat transfer, mass transfer); ICAR AIEEA-PG Code 18 Unit II
ICAR AICE-JRF/SRF (PhD) — Food Processing Technology, Food Safety & Quality, Processing and Food Engineering
41 Units 2 and 5 cover heat and mass transfer and design of processing machinery. Expect deeper questions on non-Newtonian flow, unsteady conduction and Heisler charts, effectiveness–NTU, and the heat–mass transfer analogy.
How our questions for ICAR AICE-JRF/SRF spread across the units of Transport Phenomena in Food Processing: Fluid Flow, Heat & Mass Transfer. Difficulty: 0 easy, 29 medium, 25 hard.
| Heat exchangers: plate, tubular and scraped-surface; LMTD and effectiveness | 6 | |
| Flow in pipes: Reynolds number, friction factor and pressure drop for Newtonian fluids | 5 | |
| Flow of non-Newtonian foods in pipes | 5 | |
| Unsteady-state heat transfer: lumped systems and Heisler charts | 5 | |
| Energy balances and steam tables | 4 | |
| Convective mass transfer | 4 | |
| Permeability through single and multilayer films | 4 | |
| Units, dimensions and dimensional analysis | 3 | |
| Fluid statics and the Bernoulli equation | 3 | |
| Steady-state conduction through slabs, cylinders and composite walls | 3 | |
| Convection: film coefficients and dimensionless numbers | 3 | |
| Radiation heat transfer | 3 | |
| Molecular diffusion and Fick's law | 3 | |
| Pumps for foods: centrifugal and positive-displacement | 2 | |
| Material balances on mixing, concentration and drying | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Which of these is NOT dimensionally consistent as written?
A. Q = m cp / ΔT
Heat (J) = kg × J/(kg K) × K; dividing by ΔT gives J/K², inconsistent. m λ gives J; hAΔT t gives J.
Further reading: Geankoplis, Transport Processes and Separation Process Principles
When scaling a mixing process from a 50 L pilot vessel to a 5,000 L production vessel, engineers commonly keep which quantity constant when the aim is similar turbulence intensity?
B. Power input per unit volume
Constant P/V is a common scale-up rule for turbulent mixing; constant rpm would give far higher power per volume in the large tank, and constant total power far lower.
Further reading: Earle, Unit Operations in Food Processing
As the saturation pressure of steam increases, its latent heat of vaporisation
D. decreases
hfg falls with rising pressure and temperature, reaching zero at the critical point; 2,257 kJ/kg applies at 100 °C.
Further reading: Singh and Heldman, Introduction to Food Engineering
Orifice plates are seldom used to meter milk in hygienic process lines mainly because they
D. are hard to clean and cause permanent pressure loss
Orifices create crevices and dead zones and large permanent losses; magnetic and Coriolis meters are preferred for hygienic duty.
Further reading: Geankoplis, Transport Processes and Separation Process Principles
For the milk at Re = 29,355 in a smooth 38 mm tube (ρ = 1,030 kg/m³, v = 1.5 m/s), using Blasius f = 0.0791 Re^−0.25 (Fanning), the pressure drop over 20 m is closest to
D. 14.7 kPa
f = 0.0791 × 29,355^−0.25 = 0.00604; ΔP = 4f(L/D)(ρv²/2) = 14,742 Pa ≈ 14.7 kPa. 3.69 kPa drops the factor 4 of the Fanning form; 59 kPa treats f as Fanning but applies an extra 4; 1.33 kPa wrongly uses the laminar f = 16/Re.
Further reading: Singh and Heldman, Introduction to Food Engineering
Insulation (k = 0.04 W/m K) on a pipe extends from r1 = 25 mm to r2 = 50 mm. With 90 °C at the inner and 30 °C at the outer surface, the heat loss per metre is closest to
B. 21.8 W/m
q/L = 2πk(T1 − T2)/ln(r2/r1) = 2π × 0.04 × 60/ln 2 = 21.8 W/m. 15.1 W/m treats the layer as a flat wall of inner area; 50 W/m uses log₁₀; 10.5 W/m multiplies by ln 2.
Further reading: Incropera and DeWitt, Fundamentals of Heat and Mass Transfer
Milk with Re = 29,000 and Pr = 13 is heated in a 38 mm tube (k = 0.55 W/m K). Using Dittus–Boelter for heating, Nu = 0.023 Re^0.8 Pr^0.4, the film coefficient is closest to
B. 3,450 W/m² K
Nu = 0.023 × 29,000^0.8 × 13^0.4 = 238; h = Nu k/D = 238 × 0.55/0.038 = 3,450 W/m² K. The 0.3 exponent is for cooling; 238 is Nu itself; 16.5 inverts k/D.
Further reading: Incropera and DeWitt, Fundamentals of Heat and Mass Transfer
A food slab (k = 0.5 W/m K, ρ = 1,000 kg/m³, cp = 3,600 J/kg K) of half-thickness 20 mm is heated for 30 min. The Fourier number is about
C. 0.62
α = k/ρcp = 1.39e-07 m²/s; Fo = αt/L² = 1.39e-07 × 1,800/0.02² = 0.62. 0.156 uses the full thickness 40 mm; 0.01042 uses 30 s; 2.5 uses 10 mm.
Further reading: Incropera and DeWitt, Fundamentals of Heat and Mass Transfer
A counter-current heat exchanger has equal heat capacity rates (Cr = 1) and NTU = 2.0. Its effectiveness is
B. 0.667
For Cr = 1, ε = NTU/(1 + NTU) = 2/3 = 0.667. 0.865 is 1 − e^−2, valid only when Cr = 0; 0.500 is the co-current limit; 1.000 would need infinite NTU.
Further reading: Incropera and DeWitt, Fundamentals of Heat and Mass Transfer
In an exchanger, Cmin = 3,900 W/K, hot inlet 90 °C and cold inlet 10 °C, effectiveness 0.80. The heat transferred is closest to
D. 250 kW
Qmax = Cmin(Th,in − Tc,in) = 3,900 × 80 = 312 kW; Q = 0.80 × 312 = 250 kW. 312,000 kW is Qmax with a unit slip; 390 kW divides by 0.80; 200 kW applies the effectiveness twice.
Further reading: Incropera and DeWitt, Fundamentals of Heat and Mass Transfer
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